The present invention provides a panel with improved insulating characteristics and an improved method for making an insulated panel.
Various methods have been used to produce foam filled wood stud walls. One particular method, developed by the Assignee of the present invention, is particularly suited to prefabricated walls and is described in U.S. Pat. No. 5,273,693. In that method, a half completed stud wall is introduced into an apparatus comprising a backplate and a moveable dam having a removable sheet and a compressible membrane. The exterior sheathing of the stud wall is placed against the backplate. The stud wall is backed with any suitable exterior sheathing, such as asphalt-impregnated fiber board. The removable sheet is draped over the interior of the stud wall. The compressible membrane is placed over the removable sheet and the moveable dam urges the backplate, stud wall, removable sheet and compressible membrane together. The compressible membrane forms a seal between the dam and the studs and is urged into the wall cavity reducing the volume of the cavity.
A foam or foam-forming mixture is introduced between the sheathing and the moveable dam having the removable sheet and the compressible membrane, which is temporarily positioned against the interior side of the studs. The foam or foam-forming mixture is introduced by a “spray-pour” method. In this type of method, a spray-type urethane foam is injected between the exterior sheathing and the dam using an atomizing spray nozzle having a tube to direct the trajectory of the spray. The foam is then permitted to rise freely between the sheathing and the dam and is allowed to set.
After allowing sufficient setting time to elapse, the dam is moved to the next upper unfilled section of the stud wall while the removable sheet and the compressible membrane are unrolled in advance of the moveable dam and the next bath of foam or foam-forming mixture is introduced into the wall. The wall can therefore be filled in a series of spray-pours.
This method produced a foam insulated wall panel with excellent thermal performance and a uniform planar finish on the interior surface. However, the application of urethane foam is a highly exothermic process and during the curing phase these panels are sometimes subject to some distortion.